Various polyester resins and blends thereof can be useful as engineering resins. Different polyester resins have useful properties and various performance characteristics, and there is an on-going demand for polyester.
The mechanical properties and heat resistance of polyester resin can be improved by adding inorganic reinforcing material such as glass fiber. Glass fiber reinforced polyester resin has been used in structural materials and interior and exterior parts of an automobile.
Recently, polyester resin has received interest as a material for use in LEDs (light emitting diodes) and EL (electro luminescence) devices, because polyester has excellent energy efficiency and energy lifespan.
For example, modified polyester resin reinforced by glass fiber and including benzene rings in the main chains of the polyester has been used in LED components requiring excellent energy efficiency and energy lifespan, such as reflectors, reflector cups, scramblers and LED housings. Polyester resin used in LEDs should exhibit high heat resistance during the manufacture of a light emitting diode, excellent reflectance with an initial high whiteness index, minimal deterioration of whiteness resulting from yellowing, and the ability to block the flow of electricity.
LEDs generally include a semiconductor emitting a light, a lead wire, a reflector as a housing, and a transparent sealing product sealing a semiconductor. Among these, the reflector can be made by various materials such as ceramic or heat resistant plastics. Productivity, however, of ceramics can be problematic, and heat resistant plastic can have decreased optical reflectance resulting from a change in color during the injection molding process.